The present invention relates to a device for use with Nuclear Magnetic Resonance Imaging Apparatus (known as MRI). Such a device would be for carrying out an interventional activity such as a biopsy.
Whilst MRI is used to simply visualise the internal structure of the human body in order to aid the diagnosis of the patient""s condition it is also possible to carry out interventional activities such as a biopsy in those situations where the relevant part of the patient""s body is accessible. This could be where a so-called open MRI system is being used, e.g. one using two spaced apart coils or a C-shaped magnet or one in which the axial length of the field magnet, and thus its bore into which the patient fits, is sufficiently short to allow such access. Such systems are hereinafter referred to as xe2x80x9caccessiblexe2x80x9d systems.
The combination of such accessible magnet systems, along with the commercial availability of MR-compatible biopsy needles, has opened up the possibility of exploiting the excellent soft tissue contrast of MR imaging to visualise lesions in order to guide biopsies.
In order to accurately position the biopsy needle a so-called stereotaxy device is employed, this device enabling points in space within the patient to be accurately defined. For example a frame stereotaxy device comprises a physical three-dimensional framework which is clamped to the patient, e.g. to the patient""s head, so that any point in space within the patient""s head can be accurately defined on the x, y and z axes in relation to the framework. A frameless stereotaxy device achieves the same effect but instead of using a physical framework to define the x, y and z coordinates it employs optical or ultrasound means.
One known approach is to place small MR-visible markers on the anatomy surface and collect a volume image of the region. The patient is then withdrawn from the bore of the magnet. A hand-held biopsy needle device with two ultrasound emitters set at fixed distances from the biopsy needle tip can be located in space by a fixed array of microphones and by pointing at the fiducial markers, the MR image information can be mapped onto the current position of the patient and hence the position and orientation of the biopsy needle can be displayed on the MR images.
In an accessible magnet system the operator can manipulate a biopsy needle device actually at the imaging region. By using an optical frameless stereotaxy system, for example, suitably mounted on the machine it is then possible for the current position of the device to set the MR imaging slice position in a dynamic way and hence guide the biopsy process.
In U.S. Pat. No. 5,365,927, it has been proposed to provide a pointing device to indicate the position and orientation of a plane in which an image is to be acquired. MR tracking devices, such as those disclosed in U.S. Pat. No. 5,271,400 may be used to track the position of the pointer.
The present invention is concerned with providing a device for use with an MR stereotaxy system, the latter to be used at the imaging region of an MR scanner such that the device can be guided in a very simple and interactive way using the magnet gradient system as the measurement system without the need for additional hardware. The particular application envisaged here is breast biopsy although the same device could be used by biopsy in other regions, for instance the liver or brain. The invention can also be used in connection with interventionalist devices other than biopsy devices, such as imaging coils adapted for insertion into body passages such as endorectal imaging coils.
The present invention provides a method of displaying the position and orientation of a medical implement in relation to a patient, the medical implement being provided with at least two positioning elements each comprising MR active samples with respective r.f. receiver coils carried by the samples, the receiver coils being connected to separate receiver channels of magnetic resonance processing electronics, which method comprises performing a cycle comprising the steps of applying an r.f. excitation pulse and magnetic field gradients, processing the magnetic resonance signals to locate the positions of the elements, applying r.f. excitation pulse and magnetic field gradients to image a region of the patient dependent on the location of a desired part of the medical instrument, and displaying the region of the patient with the instantaneous position of the medical instrument superimposed on an MR image, moving the medical implement and repeating the cycle.
The present invention also provides an apparatus for displaying the position and orientation of a medical implement in relation to a patient, the medical implement being provided with at least two positioning elements comprising MR active samples with respective r.f. receiver coils carried by the samples, the receiver coils being connected to separate receiver channels of magnetic resonance processing electronics, which comprises r.f. excitation pulse and magnetic field gradient means for exciting and detecting resonance, means for processing the magnetic resonance signals to locate the positions of the elements and to image a region of the patient dependent on the location of a desired part of the medical instrument, and display means for displaying the region of the patient with the instantaneous position of the medical instrument superimposed on it.
According to one aspect of the invention there are three positioning elements so located in relation to the body portion and to one another that when energised they generate signals which enables the position and orientation of the device to be determined and/or visualised with respect to the x, y and z axes.
According to a second aspect of the invention the liquid is doped water.
According to a third aspect of the invention each positioning element also includes a capacitor electrically connected to the auxiliary coils.
According to a fourth aspect of the present invention the body portion is made from a plastic material.
According to a fifth aspect of the present invention each reservoir comprises a glass phial.